8.1 Metabolism Flashcards
What can metabolic pathways form?
chains or cycles
What is a metabolic pathway?
chemical changes that happen in a sequence of small steps
What is activation energy?
energy requied to reach the transition state then to the product
is used to break or weaken bonds in the substrates
What would a graph showing activation energy with and without enzymes look like?
How do enzymes affect activation energy?
- the binding to a substrate lowers the overall energy level of the transition state
- activation energy is therefore reduced
- the rate of reaction is greatly increased
What are the two main types of inhibitors?
Competitive and non-competitive inhibitors
What are competitive inhibitors
they interfere with the active site so that the substrate cannot bind
What are non-competitive inhibitors?
they bind at a the allosteric site of the enzyme and cause a change of shape in the enzyme so that the enzyme cannot bind to the substrate
How would a graph showing the effect of a normal, competitive, and a non-competitive enzyme on rate of reaction look like?
What is end-product inhibition?
when the end product of the pathway acts as an inhibitor by binding to the allosteric site
the pathway works rapidly in cells with a shortage of end product but can be switched off completely in cells where there is an excess
reactions often do not go to completion - insead equilibrium position is reached (substrate and product)
If the conc of products increases, the reaction will eventually slow down and stop
End-product inhibition prevents a build-up of intermediate products
What is an example of end-product inhibition?
through 5 reactions
* Amino acid threonine is converted to isoleucine
* as the concentration of isoleucine builds up, it binds to the allosteric site of the first enzyme in the chain, threonine deaminase, thus acting as a non-competitive inhibitor
How can the rate of an enzyme-controlled reaction be measured?
measure the rate of disappearance of a substrate/product
